GB792558A - Manufacture of organic peroxides - Google Patents

Abstract

Peroxides of the formula <FORM:0792558/IV (b)/1> where Ar is an aryl radical, R1, R2, R3 and R5 are aliphatic groups, and R5 is an aliphatic or an aryl radical, are made by reacting a hydroperoxide of the formula <FORM:0792558/IV (b)/2> with a carbinol of the formula <FORM:0792558/IV (b)/3> in a molar proportion of hydroperoxide to carbinol of from 1:0.8 to 1:1.6 and at a temperature below 60 DEG C. in solution in an aliphatic carboxylic acid which is a solvent for both reaction components and for water and in the presence of perchloric acid or sulphuric acid as catalyst, and rendering the catalyst in the reaction mixture ineffective before recovering the peroxide. Aliphatic carboxylic acid solvents mentioned are formic, acetic, propionic and butyric acids. The reaction may be effected between room temperature and 35 DEG C. with a hydroperoxide-carbonol mixture in a solution of up to 50 per cent by weight and free from water. The starting materials may be mixtures of pure hydroperoxides and carbinols, or crude hydroperoxides from the oxidation of aromatic hydrocarbons with molecular oxygen followed by removal of unreacted hydrocarbon, or crude carbinols from the chemical reduction or hydrogenation of hydroperoxides. In a preferred embodiment, a hydroperoxide-containing reaction mixture prepared by oxidation is divided into two parts, one part being reduced to the carbinol and returned to the mixture. Alternatively, the hydroperoxide-containing mixture may be hydrogenated until half is converted to the carbinol. After the condensation reaction, the catalyst is rendered ineffective by adding basic alkali-metal or alkaline earth metal compounds or alkali-metal or alkaline earth metal salts of the aliphatic acid used as solvent, and the acid solvent is then distilled off and the residue added to water or dilute aqueous alkali to separate solid peroxide. The acid solvent may be re-used after distillation. Alternatively, the condensation reaction mixture may be added directly to water. The crude product is pressed out to remove oil and recrystallized. The oil contains unreacted carbinol and may be recycled after optional distillation. In examples: (1) phenyl dimethyl carbinol, obtained by reducing cumene hydroperoxide with aqueous sodium sulphite, is reacted with cumene hydroperoxide in acetic acid and in the presence of perchloric acid to give dicumyl peroxide; (2) dicumyl peroxide is similarly obtained from a starting mixture made by oxidizing cumene with molecular oxygen at elevated temperature, removing cumene, dividing into 2 parts, hydrogenating one part in the presence of palladium on activated alumina and re-combining it with the other part; (3) sulphuric acid is used instead of perchloric acid.